This is more of a bug report, or at least a curious observation on my end:
I had a problem with some of my images. Most were resized as expected using the transformation query string. Some of them did not work.
I tried renaming ( dump spaces in the filenames ), deleting, re-uploading, … since I uploaded a few images before I had Git LFS / NLM enabled. So I thought it might be something to do with indexing, content-type, … Browser inspector told me the file was of type image/jpeg etc. Everything looked fine. Except the end result.
The fix was: renaming the file extension from jpeg to jpg.
These images are exports of the macOS Photos app, taken with iPhone and are 4-5Mb in size.